In continuation of our study on the association between the long-term success of aortocoronary vein bypass and the presence and extent of heart disease risk factors, we intend to investigate the reasons for a relative "under-representation" of women in the patient population requiring the operation (women make up less than 15% of the patients). The histologic changes of the vein grafts of patients who have died one year or longer after the bypass operation or needed a second bypass operation will be studied. Special attention will be directed toward development of atherosclerosis in the transplanted veins.